1. Field of the Invention
The present invention relates generally to prosthetics, and, more specifically to an attachment system used in the donning/doffing of a socket onto a residual limb. The present invention more particularly relates to an attachment system that requires little or no clearance inside the socket between the socket and the residual limb, that controls rotation of the prosthesis, and that may be used with a suction-fit socket system. The invented attachment system extends from the side of a liner on the user""s limb, through an aperture in the socket, to the outer side of the socket, substantially proximal on the limb and on the socket relative to conventional more xe2x80x9cdistalxe2x80x9d attachment devices. Therefore, the invented attachment may properly be called an exterior, proximal attachment device for a prosthesis.
2. Related Art
For years, many different methods have been used to retain or xe2x80x9csuspendxe2x80x9d a prosthetic limb on an amputee""s residual limb. Gravitational and other forces, for example, from movement of the limbs, tend to cause separation between the prosthetic limb and the patient""s residual limb during use. This happens, for example, during the swing phase of gait, when a prosthetic leg is additionally subjected to centrifugal forces. Patients have routinely worn a variety of belts, straps, cuffs, and harnesses to retain their prosthetic limbs against separation from the limb during these periods. But such devices are often inconvenient and may tend to cause chafing against the patient""s body, giving rise to sores and abrasions.
The manner in which an artificial limb is suspended and/or attached to the residual limb determines the amount of control an amputee has over the prosthesis. Therefore, by improving suspension/attachment without adding weight and excessive mechanism, the amputee may obtain improved comfort, convenience, and suspension mobility.
A common approach to tackling this problem has led to the design of a roll-on suction liner, which is rolled on the residual limb on its proximal end, and attached at its distal end to a socket or artificial limb. The liner, which is usually fabricated from silicone, or some other gel form, fits snugly over the residual limb and is, in turn, enveloped, especially at its distal end, by the socket of the prosthesis, which is also called a xe2x80x9chard socket.xe2x80x9d This suspension method is very advantageous for the amputee. It gives the amputee the ability to better control the prosthesis and provides for useful sensory or proprioceptive feedback. Suction suspension also makes a prosthesis feel lighter, compared to other forms of suspension. Unfortunately, only a small percentage of amputees can successfully and comfortably wear a liner without another form of suspension. Typically, therefore, the socket liner is equipped with a detachable attachment component, usually at its distal end, which mates with a locking device, typically in the distal inside region of the socket, and which thereby secures the residual limb to an artificial limb. Hence, the name xe2x80x9cdistalxe2x80x9d attachment or lock is used for this typical design. The locking device in the distal end of the socket generally employs a spring-loaded clutch mechanism or a pin-lock mechanism inside the socket, which locks onto the liner attachment component. The attachment component on the liner is typically a cylindrical barb-shaped structure or frictionally-retained pin.
One problem associated with such designs is the tugging or pull on the distal end of the limb. Most of these locks are not air tight, thus allowing air to flow into the hard socket and to eliminate the xe2x80x9csuction.xe2x80x9d When this happens, the only suspension is the pin, which is a traction suspension, rather than suction. In cases where prosthetic socks are worn outside the liner, there is also a risk of the user""s limb being trapped in the socket if the sock is forced into the lock mechanism and then gets stuck. In these incidents, most patients are forced to make emergency trips to their practitioner to be able to get the prosthetic off. Also, the locking device and attachment component cooperate in such a way to permit the barb or pin to lock in a plurality of longitudinal positions, which affects the overall length of the prosthesis. This can make it difficult for the patient to consistently achieve the same prosthetic configuration when the residual limb and the artificial limb are articulated. It should be further noted that, by weight of the lock being added at the distal end of the residual limb or near the distal end of the socket, this can make the prosthetic device feel heavier because of a xe2x80x9clever armxe2x80x9d effect, than if the same weight were placed more proximally. Additionally, many amputees, whether because of the length of their residual limb or their height, do not have room in the suction liner-socket-prosthesis combination for a distal locking mechanism. Or, additionally, use of a distal lock may limit what other prosthetic components that patient may use.
Also, despite the large number of suspension options available, none of the above-mentioned devices act to eliminate rotation between the hard socket and the suction liner. In an attempt to alleviate the rotation problem, a design called a xe2x80x9cquad socketxe2x80x9d has been used for many years. The quad socket is shaped in a square manner more than a cylindrical manner, and forcing the xe2x80x9ccylindricalxe2x80x9d limb to fit tightly in this square receptacle makes the prosthesis less apt to rotate on the limb, much as if you made a wheel square. Unfortunately, this is not a very comfortable position for the limb. Today, therefore, there has been a trend toward more naturally-shaped sockets, making rotation control even more difficult.
Therefore, there is still a need for an improved attachment system for prosthetics. Also, there is a need for improving retention of the stump in the socket without sacrificing the patient""s comfort and without comprising on expense, weight and simplicity of use of the prosthesis. There also is a need for improving rotation control, which will improve the patient""s overall comfort and agility.
The present invention is an attachment system or xe2x80x9clatch mechanismxe2x80x9d for connecting a prosthesis to a residual limb of the user. Preferably, the attachment system extends from the side surface of a liner on a residual limb to the outside side surface of a hard socket fitted around the liner and limb. Preferably, the attachment system includes a tab system that connects to the outer side surface of the liner, which tab system extends into the socket along-side the limb and the socket, and through an aperture in the sidewall of the socket. Preferably, the tab system further extends to a lock connected to the outer side surface of the socket, typically about midway or more, proximally, on the outside surface of the socket. Thus, the attachment system is located proximally (nearer the user""s torso rather than farther out from the torso) and externally relative to conventional distal components that are typically inside the socket and at the very end (distally) of the limb, respectively. Mounting the lock proximally rather than conventionally in the xe2x80x9cbottomxe2x80x9d of the inside xe2x80x9cwellxe2x80x9d of the socket, eliminates the need for extra room inside the socket for the lock component. This also prevents the pulling or tugging on the distal end of the limb that can cause discomfort. The lock is also mounted externally, allowing it to be easily reached by the user, easily maintained, and/or easily retrofit as an add-on feature to existing hard sockets. Also, the externally-mounted lock eliminating jams caused by socks that are often worn over the roll-on liners. Any opening through the socket that is used in the mounting and connecting of the tab to the lock can then preferably be easily resealed by a gel suction wrap/cover, or other air-tight wrap or plug that preferably encases the lock mechanism and aperture, thus allowing and maintaining a xe2x80x9csuctionxe2x80x9d fit between the socket and the liner that improves the function of the prosthetic as discussed above. In this way, a combination of the invented strap and lock system and a suction fit provide superior retention of the artificial limb on the user.
The preferred tab system includes a disk member or xe2x80x9cumbrellaxe2x80x9d that may be adhesively held on the surface of the liner, and an elongated strap or xe2x80x9ctabxe2x80x9d that extends down distally from the umbrella and longitudinally a short distance along the side surface of the limb. The tab may be secured to the umbrella in such a way that its exact angle relative to the limb""s longitudinal axis may be adjusted as desired and then locked in place, for example, by tightening of a bolt. This allows for swinging the tab slightly to a different angle to properly reach and latch into the latch mechanism, so that perfect pre-placement of the umbrella and lock are not absolutely required, but rather, some adjustability for custom fitting is provided. The lock is preferably a buckle-style device, with a spring-biased member with, for example, one or more sharp edges, that frictionally engage transverse detents located between transverse raised ridges on the tab surface. Thus, the tab is inserted into the buckle to the extent desired by the user, and, in a ratchet-like action, the sharp edges wedge into the transverse detents and secure the tab from being pulled out or away from the latch mechanism. Thus, the tab is anchored in the latch mechanism, and the socket is held closely on the residual limb until the user chooses to unbuckle the latch mechanism. Therefore, the latch mechanism is easily accessible, effective, simple, and easy to use. The versatility and simplicity, and non-interfering design of the invented latch mechanism help provide reliable and comfortable suspension for an artificial limb on a great number of persons with limb deficiency.